GETOPT(3)GETOPT(3)
NAME
getopt - get option letter from argv
SYNOPSIS
int getopt (argc, argv, optstring)
int argc;
char **argv;
char *optstring;
extern char *optarg;
extern int optind;
DESCRIPTION
Getopt returns the next option letter in argv that matches a
letter in optstring. Optstring is a string of recognized
option letters; if a letter is followed by a colon, the
option is expected to have an argument which may or may not
be separated from it by white space. Optarg is set to point
to the start of the option argument on return from getopt.
Getopt places in optind the argv index of the next argument
to be processed. Since optind is external, it is normally
initialized to zero automatically before the first call to
getopt.
Option letters appear in nonempty clusters preceded by `-'.
When all options have been processed (i.e., up to the first
non-option argument), getopt returns EOF. The special
option `--' may be used to delimit the end of the options;
EOF will be returned, and `--' will be skipped.
DIAGNOSTICS
Getopt prints an error message on stderr and returns a ques-
tion mark ('?') when it encounters an option letter not
included in optstring.
EXAMPLE
This fragment processes arguments for a command that can
take option a and option f, which requires an argument.
main (argc, argv) char **argv;
{
int c;
extern int optind;
extern char **optarg, **ifile;
while ((c = getopt (argc, argv, "af:")) != -1)
switch (c) {
case 'a': aflg++;
break;
case 'f': ifile = optarg;
break;
GETOPT(3)GETOPT(3)
case '?': errflg++;
}
if (errflg) {
fprintf (stderr, "usage: . . . ");
exit (2);
}
for( ; optind < argc; optind++) {
if (access (argv[optind], 4)) {
...